Binding of chloroplast signal recognition particle to a thylakoid membrane protein substrate in aqueous solution and delineation of the cpSRP43-substrate interaction domain

• Verfasst von: Cain, Peter [VerfasserIn]
• Verfasst von: Holdermann, Iris Valerie [VerfasserIn]
• Verfasst von: Sinning, Irmgard [VerfasserIn]
• Verfasst von: Johnson, Arthur E. [VerfasserIn]
• Verfasst von: Robinson, Colin [VerfasserIn]
• Titel: Binding of chloroplast signal recognition particle to a thylakoid membrane protein substrate in aqueous solution and delineation of the cpSRP43-substrate interaction domain
• Verf.angabe: Peter Cain, Iris Holdermann, Irmgard Sinning, Arthur E. Johnson and Colin Robinson
• E-Jahr: 2011
• Jahr: June 14 2011
• Umfang: 7 S.
• Fussnoten: Im Titel ist die Zahl 43 tiefgestellt ; Gesehen am 27.06.2022
• Titel Quelle: Enthalten in: Biochemical journal
• Ort Quelle: London : Portland Press, 1906
• Jahr Quelle: 2011
• Band/Heft Quelle: 437(2011), 1, Seite 149-155
• ISSN Quelle: 1470-8728
• DOI: doi:10.1042/BJ20110270
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 180786796X

Abstract

A cpSRP [chloroplast SRP (signal recognition particle)] comprising cpSRP54 and cpSRP43 subunits mediates the insertion of light-harvesting proteins into the thylakoid membrane. We dissected its interaction with a full-length membrane protein substrate in aqueous solution by insertion of site-specific photo-activatable cross-linkers into in vitro-synthesized Lhcb1 (major light-harvesting chlorophyll-binding protein of photosystem II). We show that Lhcb1 residues 166-176 cross-link specifically to the cpSRP43 subunit. Some cross-link positions within Lhcb1 are in the ‘L18’ peptide required for targeting of cpSRP substrates, whereas other cross-linking positions define a new targeting signal in the third transmembrane span. Lhcb1 was not found to cross-link to cpSRP54 at any position, and cross-linking to cpSRP43 is unaffected by the absence of cpSRP54. cpSRP43 thus effectively binds substrates autonomously, and its ability to independently bind an extended 20+-residue substrate region highlights a major difference with other SRP types where the SRP54 subunit binds to hydrophobic target sequences. The results also show that cpSRP43 can bind to a hydrophobic, three-membrane span, substrate in aqueous solution, presumably reflecting a role for cpSRP in the chloroplast stroma. This mode of action, and the specificity of the cpSRP43-substrate interaction, may be associated with cpSRP's unique post-translational mode of action.